serializeDeserialize.js

// Preorder traversal DFS: TC:O(n) SC: O(n)
let i = 0;
function serialize(root) {
    let list = [];
    serializeDFS(root, list);
    return list.join(",");
}

function serializeDFS(node, list) {
    if (node == null) {
      list.push("N");
      return;
    }
    list.push(node.value);
    serializeDFS(node.left, list);
    serializeDFS(node.right, list);
}

// DFS: TC:O(n) SC: O(n)
function deserialize(data) {
    let tokens = data.split(",");
    return deserializeDFS(tokens);
}

function deserializeDFS(tokens) {
    let token = tokens[i];
    if (token === "N") {
      i++;
      return null;
    }
    let node = new TreeNode(token);
    i++;
    node.left = deserializeDFS(tokens);
    node.right = deserializeDFS(tokens);

    return node;
}

class TreeNode {
  constructor(value) {
    this.left = null;
    this.right = null;
    this.value = value;
  }
}


function printTree(root) {
    if(root === null) return;
    console.log(root.value + " ");
    printTree(root.left);
    printTree(root.right);
}

  let root = new TreeNode(0);
  root.left = new TreeNode(1);
  root.right = new TreeNode(2);
  root.left.left = new TreeNode(3);
  root.left.right = new TreeNode(4);
  root.right.left = new TreeNode(5);
  root.right.right = new TreeNode(6);

  let serializeStr = serialize(root);
  console.log(serializeStr);
  printTree(deserialize(serializeStr));

  i=0;
  let serializeStr1 = serialize(null);
  console.log(serializeStr1);
  console.log(deserialize(serializeStr1));